1. Technical Field
The present invention relates to an electromagnetic flowmeter for measuring the flow rate of an electroconductive fluid such as a liquid metal flowing in a tubular channel.
2. Description of the Prior Art
An electromagnetic flowmeter for a liquid metal described in Japanese Patent Laid-Open No. 10-176937 for example is known as a conventional electromagnetic flowmeter. This electromagnetic flowmeter has a pair of magnets which are disposed on opposite sides of a tubular channel for flow of a liquid metal, and which form a magnetic field in a direction perpendicular to a longitudinal axis of the tubular channel, and a pair of electrodes for measuring an electromotive force generated by the movement of the liquid metal across the magnetic field. The flow rate of the liquid metal is obtained from the measured value of the electromotive force.
Since the above-described conventional electromagnetic flowmeter is constructed so as to have magnets placed on opposite sides of a tubular channel, there are problems with its use in the case of performing a measurement on a large-diameter pipe line such as that in a fast breeder reactor for practical use. That is, there is a need to install an excitation device of an increased size according to the external size of the pipe line and it is difficult to prepare the necessary installation space. Also, the manufacturing cost of the excitation device is high.
The above-described conventional electromagnetic flowmeter is assumed to be used for measurement on tubular channels in cylindrical form and is capable of accurately measuring the flow rate of a liquid in a tubular channel with comparatively high accuracy if the tubular channel is generally cylindrical. However, the conventional electromagnetic flowmeter is incapable of accurately measuring the flow rate of a liquid in a tubular channel in some other form, e.g., one having an annular sectional shape, and it is difficult to apply the conventional electromagnetic flowmeter to measurement in such a case.